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FieldbusFOUNDATION FieldbusOverviewFOUNDATION Fieldbus Overview

July 2000 EditionPart Number 322857A-01

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© National Instruments Corporation v Foundation Fieldbus Overview

Contents

Chapter 1What Is Fieldbus?

Related Documentation..................................................................................................1-1The Fieldbus Foundation ...............................................................................................1-2Uses of Fieldbus.............................................................................................................1-2The Fieldbus Network ...................................................................................................1-3FOUNDATION Fieldbus Communication Protocols...........................................................1-4FOUNDATION Fieldbus Concepts......................................................................................1-5

Links ................................................................................................................1-5Devices ............................................................................................................1-6Blocks and Parameters ....................................................................................1-8Linkages ..........................................................................................................1-8Loops ...............................................................................................................1-8

Multiple Loops..................................................................................1-9

Chapter 2FOUNDATION Fieldbus Technology and Layers

Physical Layer................................................................................................................2-2Communication Stack....................................................................................................2-2

Virtual Field Devices.......................................................................................2-3User Layer......................................................................................................................2-3

Device Descriptions.........................................................................................2-4Blocks ..............................................................................................................2-5

Resource Block .................................................................................2-5Transducer Blocks.............................................................................2-5Function Blocks ................................................................................2-6

AI (Analog Input) ...............................................................2-7AO (Analog Output) ...........................................................2-7PID (Proportional–Integral–Derivative).............................2-7DI (Discrete Input)..............................................................2-7DO (Discrete Output) .........................................................2-7CDO (Complex Discrete Output) .......................................2-8

Function Block Parameters ...............................................................2-8Function Block Applications ..............................................2-10Function Block Modes........................................................2-10The Function Block MODE_BLK Parameter ....................2-11

Objects.............................................................................................................2-11

Contents

Foundation Fieldbus Overview vi www.ni.com

Chapter 3Fieldbus Communication

Scheduled Communication on the Bus.......................................................................... 3-1Cascading Blocks .......................................................................................................... 3-2

Parameter Connections for Cascade Mode ..................................................... 3-2

Chapter 4Wiring and Connections

Termination ................................................................................................................... 4-2Link Configuration ........................................................................................................ 4-3

Chapter 5National Instruments Fieldbus Products

Hardware Products ........................................................................................................ 5-1Software Products.......................................................................................................... 5-1Choosing Configuration Software................................................................................. 5-2Choosing an HMI Package............................................................................................ 5-3

Common Features of Both BridgeVIEW and Lookout .................................. 5-3Typical BridgeVIEW Applications................................................................. 5-3Typical Lookout Applications ........................................................................ 5-3Using Both BridgeVIEW and Lookout in an Application.............................. 5-4

Appendix ATechnical Support Resources

Glossary

Index

© National Instruments Corporation 1-1 Foundation Fieldbus Overview

1What Is Fieldbus?

This chapter gives a short overview of FOUNDATION Fieldbus and describesthe parts of a FOUNDATION Fieldbus network. Refer to the Glossary for moreexplanation of Fieldbus terms and concepts. The generic term fieldbusrefers to any bus that connects to field devices. This includes FOUNDATION

Fieldbus, CAN, DNET, and Profibus. In this manual, the term Fieldbusrefers specifically to the FOUNDATION Fieldbus.

Related DocumentationGeneral Fieldbus Websites

• Fieldbus Foundation—Responsible for the definition of theFOUNDATION Fieldbus specification. www.fieldbus.org

• Relcom, Inc.—Wiring and test equipment for FOUNDATION Fieldbus.www.relcominc.com/fieldbus

• Fieldbus, Inc.—Device developers and FOUNDATION Fieldbusconsulting. www.fieldbusinc.com

Fieldbus system development documentation

• Fieldbus Foundation resources

– Wiring and Installation 31.25 kbit/s, Voltage Mode, Wire Medium

• Relcom, Inc. Fieldbus resources online

– Wiring Design and Installation Guide

– Online Tutorial

– FAQ

– Sample Fieldbus Topologies

• Fieldbus Standard for Use in Industrial Control Systems, Part 2,ISA-S50.02.1992

Fieldbus device development documentation

• How to Develop Your First FOUNDATION Fieldbus Device, availablefrom the Fieldbus, Inc. website at www.fieldbusinc.com

Chapter 1 What Is Fieldbus?

Foundation Fieldbus Overview 1-2 www.ni.com

• Foundation Specification: 31.25 kbit/s Physical Layer Profile for theFOUNDATION Fieldbus Physical Layer Specifications

• FOUNDATION Fieldbus specification Function Block ApplicationProcess, Part 1

• FOUNDATION Fieldbus specification Function Block ApplicationProcess, Part 2

• FOUNDATION Fieldbus specification System Architecture

• IEC Standard 1158-2 and ISA Standard ISA S50.02

The Fieldbus FoundationThe Fieldbus Foundation is the organization that defines the FOUNDATION

Fieldbus specification and certifies products to be compliant with thestandard. The FOUNDATION Fieldbus standard defines the way you can bringnew devices into the network, set them up, and configure them. Anycompany with the proper resources can make a FOUNDATION Fieldbusdevice (if it passes the Conformance Test) that will work with all otherFOUNDATION Fieldbus-certified devices and software.

The goal of the Fieldbus Foundation is to help create products that use arobust industrial network based on existing standards and other proventechnologies and to standardize using those sources. FOUNDATION Fieldbusis an open standard, which allows you to use FOUNDATION Fieldbus productsfrom different vendors interchangeably. For more information about theFieldbus Foundation, refer to their website at www.fieldbus.org

Uses of FieldbusFOUNDATION Fieldbus is used in process control and monitoring. Processcontrol refers to low-speed, continuous processes like flow control,temperature control, and tank level control. These types of processes aretypically found in places like oil refineries, chemical plants, and papermills. FOUNDATION Fieldbus can also be used for low-speed monitoring overlong distances (up to 1900 m per link without repeaters).

FOUNDATION Fieldbus implements distributed control, which means thatcontrol is done by the devices instead of by a monitoring computer. Input,output, and process control devices configured on a Fieldbus network canrun independently of a computer system.



National Instruments FOUNDATION Fieldbus products can be used to createa FOUNDATION Fieldbus system. For example, National Instruments does notmake valves or pressure transmitters, but with National Instruments tools,you can make a valve and pressure transmitter from third parties worktogether over a FOUNDATION Fieldbus network to implement level control ina tank. You can use National Instruments Lookout with NationalInstruments FOUNDATION Fieldbus boards to develop the Human MachineInterface (HMI) for the resulting control system. With the NI-FBUSCommunications Manger or NI-FBUS Configurator software, you can alsouse OPC to connect to third-party software packages that support OPC.

The Fieldbus NetworkFOUNDATION Fieldbus is an all-digital, two-way, multi-drop communicationsystem that brings the control algorithms into instrumentation. FOUNDATION

Fieldbus is a Local Area Network (LAN) for FOUNDATION Fieldbus devicesincluding process control sensors, actuators, and control devices. Using theNational Instruments FP-3000 FOUNDATION Fieldbus device, you canincorporate traditional 4-20 mA devices into your Fieldbus network.FOUNDATION Fieldbus supports digital encoding of data and many types ofmessages. Unlike many traditional systems which require a set of wires foreach device, multiple FOUNDATION Fieldbus devices can be connected to thesame set of wires.

FOUNDATION Fieldbus overcomes some of the disadvantages of proprietarynetworks by offering a standardized network to connect systems anddevices. A simple Fieldbus network setup is shown in the following figure.



Figure 1-1. FOUNDATION Fieldbus-Based Control System

FOUNDATION Fieldbus Communication ProtocolsFOUNDATION Fieldbus has two communication protocols. H1 transmitsat 31.25 Kbytes/s and is used to connect field devices. The NationalInstruments FP-3000 is an example of an H1 device. A second protocol,high-speed Ethernet (HSE), is also available. It uses 100 Mbit Ethernet asthe physical layer and provides a high-speed backbone for the Fieldbusnetwork. While the HSE was designed for 100 Mbit/s Ethernet, it alsoworks with 10 Mbit/s Ethernet.

Typical network topology will have HSE connections between computers,and run slower H1 links (31.25 Kbytes/s) between the devices themselves.Devices designed for HSE can be connected to HSE directly. Most devicesare designed to use one protocol or the other. You can use a bridge deviceto connect H1 and HSE links.

PersonalComputer

HSE

H1–Lower-Speed Fieldbus

Analyzer

— Pump

— Valve

— Transmitter

— Valve

— Local Display

— HandheldConfiguration Unit

Key

Bridge

H1 H1

H1



FOUNDATION Fieldbus ConceptsThis section discusses basic concepts of Fieldbus architecture. There aresix conceptual parts to a Fieldbus network: links, devices, blocks andparameters, linkages, loops, and schedules.

LinksA FOUNDATION Fieldbus network is made up of devices connected by a serialbus. This serial bus is called a link (also known as a segment). A Fieldbusnetwork consists of one or more links. Each link is configured with aunique link identifier.

Each link on the Fieldbus network connects physical devices. The devicescan be field devices (temperature transmitters, valves, and so on) or hostdevices (PCs, distributed control systems). Each physical device isconfigured with a physical device tag, an address, and a device ID. Thephysical device tag must be unique within a Fieldbus system, and theaddress must be unique within each link. The device manufacturer assignsa device ID that is unique to the device.

Figure 1-2 shows a link in a Fieldbus network.

Figure 1-2. Fieldbus Network Link

Link

Field Device

Host Device

Field Device Field Device



DevicesDevices are uniquely identified on the Fieldbus network by a characterstring name, or tag. The device tag is a configurable attribute of thedevice that usually describes the type of the device. Device tags areunique to each device on a Fieldbus network.

Another unique identifier of a device is the device ID, which includesa serial number unique to the device. The device ID is assigned by thedevice manufacturer; you cannot configure it.

There are three types of devices on a Fieldbus network: link masters,basic devices, and bridges.

• Link master—A link master device is capable of controlling thecommunications traffic on a link by scheduling the communicationon the network. Every Fieldbus network needs at least one linkmaster-capable device. A link master can be an interface board in aPC, a distributed control system, or any other device, such as avalve or a pressure transducer. Link masters need not be separatedevices; they can have I/O functionality (for example, you could buytemperature transmitters both with and without link master capability).The National Instruments FOUNDATION Fieldbus interface boards arelink master devices.

Fieldbus can operate independently of a computer system because oflink masters on the bus. Link masters have processing capability andare capable of controlling the bus. After you download a configurationto your device(s), your control loop can continue to operate—even ifthe monitoring computer is disconnected.

All of the link masters receive the same information at the time ofdownload, but only one link master will actively control the bus at agiven time. The link master that is currently controlling the bus iscalled the Link Active Scheduler. If the current Link Active Schedulerfails, the next link master will take over transparently and begincontrolling bus communications where the previous Link ActiveScheduler left off. Thus, no special configuration is required toimplement redundancy.

The Link Active Scheduler device follows the schedule downloaded toit and the other link masters during the configuration process. At theappropriate times, it sends commands to other devices, telling themwhen to broadcast data. The Link Active Scheduler also publishes timeinformation and grants permission to devices to allow them tobroadcast unscheduled (acyclic) messages, such as alarms and events,maintenance and diagnostic information, program invocation,



permissives and interlocks, display and trend information, andconfiguration.

• Basic device—A basic device is a device which is not capable ofscheduling communication. Basic devices cannot become the LinkActive Scheduler.

• Bridge—A bridge is a device that connects two Fieldbus links ofdifferent speeds, such as an H1-to-HSE bridge. Every bridge is linkmaster capable.

Note Be aware of the difference between a bridge and a gateway. While a bridge connectsnetworks of different speeds and/or physical layers, a gateway connects networks that usedifferent communications protocols.

Figure 1-3 shows these three types of devices.

Figure 1-3. Fieldbus Network Devices

Computer:Link Master

Bridge:Link Master

Basic Device Basic Device Link Master

Basic Device Link Master Link Master



Blocks and ParametersBlocks and parameters are described in the section Blocks in Chapter 2,FOUNDATION Fieldbus Technology and Layers.

LinkagesThe function blocks configured to control a process are linked, orconnected by configuration objects inside the devices. These linkagesallow you to send data from one block to another. A linkage is differentfrom a link, in that a link is a physical wire pair that connects devices on aFieldbus network, and a linkage is a logical connection that connects twofunction blocks. For more information on linkages, refer to the sectionObjects in Chapter 2, FOUNDATION Fieldbus Technology and Layers.

LoopsA loop (or control loop) is a group of function blocks connected bylinkages executing at a configured rate. Each block executes at theconfigured rate and data moves across the linkages between the blocksat the configured rate. Figure 1-4 shows an example of a control loop.

Figure 1-4. Control Loop

Block A

Input

Input Output

Block B

Input

Output

Linkage

Loop = 1 sec



Multiple LoopsIt is possible to have multiple loops running at different rates on a link.Figure 1-5 shows an example of multiple loops.

Figure 1-5. Multiple Loops Running At Different Rates

Even if loops are running at different rates, they can send each other datathrough linkages. Figure 1-6 shows an example of a linkage between twoloops. All loops on a link run within one macrocycle. A macrocycle is theleast common multiple of all the loop times on a given link. For example,the macrocycle in Figure 1-6 is 1 second.

Loop = 500 ms

Block A

Input

Block B Block C

Block D

Block E

Loop = 1 sec

Input

Output

Input

Output

Input

Input

Output Output

Output

Input

Device 1 Device 1

Device 1

Device 1

Device 2



Figure 1-6. Linkage Between Two Loops

Loop = 500 ms

Linkage

Block A

Input

Block B Block C

Block D

Block E

Loop = 1 sec

Input

Output

Input

Output

Input

Input

Output Output

Input


2FOUNDATION Fieldbus Technologyand Layers

Note The first few sections of this chapter apply only to FOUNDATION Fieldbus devicedevelopment. If you are not developing a FOUNDATION Fieldbus device, proceed to thesection User Layer.

FOUNDATION Fieldbus communication layers consists of the physical layer,the communication stack, and the user layer. Figure 2-1 shows a diagramof the Fieldbus layers compared to the Open Systems Interconnect (OSI)layered communication model. Notice that the OSI model does not definea user layer.

Figure 2-1. The Fieldbus Model and the OSI Seven-Layer Communications Model

FOUNDATION Fieldbus does not implement layers three, four, five, and six ofthe OSI model because the services of these layers are not required in aprocess control application. A very important part of FOUNDATION Fieldbusis the defined user layer, often referred to as layer eight.

Application Layer

Presentation Layer

Session LayerCommunication

Stack

Transport Layer

Network Layer

Data Link Layer

Physical Layer

7

6

5

4

3

2

1

Data Link Layer

Physical Layer

Fieldbus MessageSpecification

User Layer

Fieldbus AccessSublayer

Fieldbus ModelOSI Model

Chapter 2 FOUNDATION Fieldbus Technology and Layers


Refer to the FOUNDATION Fieldbus specifications for complete informationabout the layers of the FOUNDATION Fieldbus network.

Physical LayerThe physical layer converts digital Fieldbus messages from thecommunication stack to physical signals on the Fieldbus transmissionmedium and vice versa. See the Foundation Specification: 31.25 kbit/sPhysical Layer Profile for the FOUNDATION Fieldbus physical layerspecifications. The physical layer implements IEC Standard 1158-2 andISA Standard ISA S50.02.

Communication StackThe communication stack performs the services required to interface theuser layer to the physical layer. The communication stack consists of threelayers: the Fieldbus Message Specification, the Fieldbus Access Sublayer,and the Data Link Layer. The communication stack encodes and decodesuser layer messages and ensures efficient and accurate message transfer.

The Data Link Layer manages access to the Fieldbus through the LinkActive Scheduler by splitting data into frames to send on the physical layer,receiving acknowledgment frames, and re-transmitting frames if they arenot received correctly. It also performs error checking to maintain a soundvirtual channel to the next layer.

The Fieldbus Access Sublayer provides an interface between the Data LinkLayer and the Fieldbus Message Specification layer. The Fieldbus AccessSublayer provides communication services such as client/server,publisher/subscriber, and event distribution.

The Fieldbus Messaging Specification layer defines a model forapplications to interact over the Fieldbus. The object dictionary and thevirtual field device are important in this model. The object dictionary is astructure in a Fieldbus device that describes data that can be communicatedon the Fieldbus. You can think of the object dictionary as a lookup table thatgives information about a value (such as data type) that can be read from orwritten to a device. The virtual field device is a model for remotely viewingdata described in the object dictionary. The services provided by theFieldbus Messaging Specification allow you to read and write informationabout the object dictionary, read and write the data variables describedin the object dictionary, and perform other activities such asuploading/downloading data and invoking programs inside a device.



Within the Fieldbus Messaging Specification layer are two managementlayers called System Management and Network Management. SystemManagement assigns addresses and physical device tags, maintains thefunction block schedule for the function blocks in that device, anddistributes application time. You can also locate a device or a function blocktag through System Management.

Network Management contains objects that other layers of thecommunication stack use, such as data link, Fieldbus Access Sublayer,and Fieldbus Messaging Specification. You can read and write SystemManagement and Network Management objects over the Fieldbus using theFMS Read and FMS Write services.

Virtual Field DevicesThe virtual field device (VFD) is a model for remotely viewing datadescribed in the object dictionary. The services provided by the FieldbusMessaging Specification allow you to read and write information about theobject dictionary, read and write the data variables described in the objectdictionary, and perform other activities such as uploading/downloadingdata and invoking programs inside a device.

Each physical device on the Fieldbus can have one or more virtual fielddevices. A network configuration application can assign each virtual fielddevice a tag that is unique within the device. Most devices have only onevirtual field device. Each virtual field device has one resource block andone or more function blocks and transducer blocks. Each block should beassigned a tag that is unique within the Fieldbus system.

Note This manual assumes each device contains only one virtual field device.

User LayerThe user layer provides the interface for user interaction with the system.The user layer uses the device description to tell the host system aboutdevice capabilities. The user layer defines blocks and objects that representthe functions and data available in a device. Rather than interfacing to adevice through a set of commands, like most communication protocols,FOUNDATION Fieldbus lets you interact with devices through a set of blocksand objects that define device capabilities in a standardized way. The userlayer for one device consists of the resource block, and one or moretransducer blocks and function blocks, as illustrated in the following figure.



Figure 2-2. The User Layer

Device DescriptionsA key objective for FOUNDATION Fieldbus is interoperabilitythe ability tobuild systems comprised of devices from a variety of manufacturers to takefull advantage of both the standard and unique capabilities of every device.

Instead of requiring that device manufacturers use only a given set offunctions in a device to ensure that a system can always communicate witha new device, FOUNDATION Fieldbus uses device descriptions, whichdescribe all the functions in a device. They allow manufacturers to addfeatures beyond the standard FOUNDATION Fieldbus interface withoutfearing loss of interoperability. The device vendor supplies devicedescription files, which describe the parameters of the function andtransducer blocks contained in a device. The device description also definesattributes of parameters and blocks (such as names and help strings), rangesof values for parameters, functional information (such as menus andmethods that you can use with the device), and so on. At the devicemanufacturer’s discretion, names and help strings can even be provided inmultiple languages. The language can be set in the configuration software.Using the device description, the host in a control system can obtain the

Communication“Stack”

Fieldbus

User Layer

Physical Layer

TransducerBlock

TransducerBlock

ResourceBlock

FunctionBlock

FunctionBlock

FunctionBlock



information needed to create an interface that configures parameters,calibrates, performs diagnostics, and accomplishes other functions on thedevice.

The names of device description files are numbers, and they have .ffo and.sym file extensions.

BlocksBlocks can be thought of as processing units. They can have inputs, settingsto adjust behavior, and an algorithm which they run to produce outputs.They also know how to communicate with other blocks. The three types ofblocks are the resource block, transducer block, and function block.

Resource BlockA resource block specifies the general characteristics of the resource (orblock). This includes the device type and revision, manufacturer ID, serialnumber, and resource state. Each device has only one resource block. Theresource block also contains the state of all of the other blocks in the device.

The resource block must be in automatic mode for any other blocksin the device to execute. The resource block is a good place to starttroubleshooting if the device is not behaving as desired. It has diagnosticparameters that help you determine the cause of problems.

Transducer BlocksTransducer blocks read from physical sensors into function blocks.Transducer blocks decouple the function blocks from the hardware detailsof a given device, allowing generic indication of function block input andoutput.

The transducer block knows the details of I/O devices and how to actuallyread the sensor or change the actuator. The transducer block performs thedigitizing, filtering, and scaling conversions needed to provide the sensorvalue to the function blocks and/or makes the change in the output asdictated by the function block. Generally, there will be one transducer blockper device channel. In some devices, multiplexors allow multiple channelsto be associated with one transducer block.

Manufacturers can define their own transducer blocks. For some devices,including the National Instruments FP-3000, the functionality of thetransducer block is included in the function block. You will see no separatetransducer blocks for such devices.



Note There are many parameters that can be changed to modify the I/O functionality.

Function BlocksFunction blocks provide the control and I/O behavior.

Usually, a device has a set of functions it can perform. These functionsare represented as function blocks within the device. A function blockcan be thought of as a processing unit. Function blocks are used asbuilding blocks in defining the monitoring and control application.

The FOUNDATION Fieldbus specification Function Block ApplicationProcess defines a standard set of function blocks, including ten for basiccontrol and 19 for advanced control. Table 2-1 shows the ten functionblocks for the most basic control and I/O functions.

Not all devices contain all ten standard function blocks. Additionally,manufacturers can also define their own function blocks. A devicedescription file provided with each device tells the configuration softwareabout added function blocks. Thus, manufacturer-defined function blocksare as easy to use as the standard function blocks.

Different function blocks do different things. There can be many functionblocks present in a device at one time. Function blocks are stored in thedevice’s memory. Some devices come with specific function blocks

Table 2-1. Ten Standard FOUNDATION Fieldbus-Defined Function Blocks

Function Block Name Symbol

Analog Input AI

Analog Output AO

Bias/Gain BG

Control Selector CS

Discrete Input DI

Discrete Output DO

Manual Loader ML

Proportional/Derivative PD

Proportional/Integral/Derivative PID

Ratio RA



pre-loaded into memory. They cannot be deleted, nor can new functionblocks be added. Other devices, such as the National Instruments FP-3000,allow function blocks to be instantiated (created) and deleted as necessary.

Note Function blocks have a wide variety of parameters that can be changed to controltheir operation. See the section Function Block Parameters for more information.

You can connect the input and output of individual function blocks tospecify communication of data between blocks.

In general, the function blocks will be a layer of abstraction above thephysical I/O channels. Function blocks “talk” with transducer blocks,which deal with the details of I/O.

AI (Analog Input)The AI block reads data from a single analog input channel. This blockperforms simple filtering and scaling of the raw data to engineering unitsfrom the input channel and supports limit alarming.

AO (Analog Output)The AO block writes data to an analog output channel. This block supportscascade initialization to allow upstream control blocks to switch smoothlyfrom manual to automatic mode. It also has a faultstate behavior that allowsthe block to react if communications fail between itself and the upstreamblock.

PID (Proportional–Integral–Derivative)The PID block implements a PID control algorithm. In Fieldbus, a PIDblock must be connected to an upstream block (such as an AI block) and adownstream block (such as an AO block) before it can be used for control.These software connections are established by using host Fieldbusconfiguration software, such as the NI-FBUS Configurator.

DI (Discrete Input)The DI block reads data from discrete input channels. This block performssimple filtering and processing of the raw data from the input channel andsupports limit alarming.

DO (Discrete Output)The DO block writes to a discrete output channel. This block supportscascade initialization to allow upstream control blocks to determine the



current state of the process before assuming control. It also has a faultstatebehavior that allows the block to react if communications fail betweenitself and the upstream block.

CDO (Complex Discrete Output)The CDO block serves the same purpose as the DO block and adds anumber of parameters to support interlocking at three levels of priority.

Function Block ParametersYou can change the behavior of a block by changing the settings of itsparameters.

Function block parameters are classified as follows:

• Input parameters receive data from another block.

• Output parameters send data to another block.

• Contained parameters do not receive or send data; they arecontained within the block.

Some parameters contain multiple settings called fields. For example, acommon output parameter for many function blocks is OUT. OUT, however,is not just a value. It also contains information about the status of that

Table 2-2. CDO Block Interlock Priorities

Input(Descending Priority) Notes

Safeguard Close(SAFEGUARD_CL)

Safeguard Close takes priority over any other interlock input.

Safeguard Open(SAFEGUARD_OP)

Safeguard Open takes priority over every other interlock input and isused to force the block to an open state (Discrete_State_1).

Binary Open/Close(BINARY_OP/BINARY_CL)

BINARY_OP only functions when ENABLE_OP has a value ofDiscrete_State_1. BINARY_CL only functions whenENABLE_CL has a value of Discrete_State_1. If bothBINARY_OP and BINARY_CL are set and enabled, neither onetakes effect.

Operator Command(OP_CMD_CXO)

OP_CMD_CXO is a contained bit string parameter that has a bit forOpen and a bit for Close. Open only functions when ENABLE_OP

has a value of Discrete_State_1. Close only functions whenENABLE_CL has a value of Discrete_State_1. If both Open andClose are set and enabled, neither one takes effect.



value—whether it is good or questionable, for example. Thus, the OUTparameter actually consists of two fields, VALUE and STATUS. In thisdocumentation set, the fields of a parameter will be indicated as theParameterName.FieldName, for example, OUT.VALUE. The OUTparameter (including both VALUE and STATUS fields) is generated by theblock at the end of the block execution. This parameter is published on thebus if it is required as the input for another function block in a differentdevice. If the parameter is only required by other function blocks in thesame device, it will not be needlessly published on the bus. See the sectionScheduled Communication on the Bus in Chapter 3, FieldbusCommunication, for more information on publishing across the bus.

Figure 2-3 shows an example of a function block and its input and outputparameters that are available to other blocks.

Figure 2-3. Function Block Parameters

Note There are different input and output parameters for different uses, such as cascade,remote, and so on.

An output parameter can be linked to an input parameter of anotherfunction block. Like an output parameter, an input parameter containsfields VALUE and STATUS. The IN.STATUS is inherited from the linkedoutput parameter.

Devicewith Blocks

Input Output

Input



Contained parameters cannot be linked to an output or input parameter.Instead, they are either set internally or set by an operator. Examples ofcontained parameters are scaling parameters, alarm limits, I/O options, anderror codes.

Function Block ApplicationsThe function block application is like a program that you download to yourdevice for it to execute. How you create a function block applicationdepends on the configuration software you are using. In the NI-FBUSConfigurator, the inputs and outputs of the function blocks are wiredtogether in graphical format to create the control strategy. The NI-FBUSConfigurator also automatically creates an execution schedule for thefunction blocks. You then download the entire configuration to the device,including the function block application and schedule. When this is done,the device can begin executing the function blocks according to theschedule.

Function Block ModesOne of the more confusing aspects of Fieldbus for new users is the conceptof function block modes—what the modes are and how to get a block intothe desired mode.

The most common modes are Automatic (Auto), Cascade (Cas), Manual(Man), and Out Of Service (OOS).

• In Automatic mode, the block is using a local setpoint value in thenormal block algorithm to determine the output value.

• In Cascade mode, the block is receiving its setpoint value from anotherfunction block for use in the normal block algorithm to determine theoutput value.

• In Out Of Service mode, the block is not running at all. Normally, thismode is used during block configuration. Also, some devices requirethat the function block be in Out Of Service mode when changingcertain parameters.

• In Manual mode, the block output is not being calculated by the normalblock algorithm. The operator writes the output of the block directly.



The Function Block MODE_BLK ParameterThe MODE_BLK parameter for a function block is the parameter thatcontains information on the modes of the block. It has four fields: TARGET,ACTUAL, PERMITTED, and NORMAL. PERMITTED and NORMAL are definedby the device manufacturer.

• PERMITTED contains a list of all allowable modes for that block.

• NORMAL is the mode the device manufacturer expects the block to be induring normal use.

• ACTUAL is the current operating mode of the function block on thedevice.

• TARGET is a field that is writable by the user. Writing this field tells thedevice to change to the specified mode. The device will attempt tochange the mode. If it is successful, the ACTUAL field changes to reflectthe TARGET field.

Note If the block is not currently scheduled, it will always be in Out Of Service mode.In this case, writing the TARGET field will not change the ACTUAL field. After it attemptsto change the block from Out Of Service to the specified mode and fails, the TARGET fieldwill return to Out Of Service.

ObjectsIn addition to the blocks described, the user layer of a FOUNDATION Fieldbusdevice contains other types of objects. Objects are defined by theFOUNDATION Fieldbus specification as part of the function block applicationstructure. Some of them are presented here so that you are aware of thefeatures they offer. If you are using a configuration software package, suchas the NI-FBUS Configurator, you will not need to deal with them directly.

• Linkage object—Linkage objects define the connections between theoutputs of one block and inputs of another, whether the blocks are inthe same device or different devices.

Note If you are using the NI-FBUS Configurator, the linkage object is created implicitlywhen you wire the output of one function block to the input of another. The PID and AOare examples of function blocks that often receive their setpoints from an upstream block.



In the following diagram, there are three linkages:

– The AI block’s OUT parameter to the PID block’s IN parameter.

– The PID block’s OUT parameter to the AO block’s CAS_INparameter.

– The AO block’s BKCAL_OUT parameter to the PID block’sBKCAL_IN parameter.

Figure 2-4. Linkages

Parameters are sent across the bus when a linkage connects an outputparameter from a function block in one device to an input parameter ofa function block in another device. A block parameter in the device thatis writing to the bus is referred to as a published parameter. A blockparameter in the device that is receiving data from the bus is referredto as a subscribed parameter. In Figure 2-4, the OUT parameter of theAI block is a published parameter, and the IN parameter of the PIDblock is a subscribed parameter.

• View object—View objects allow efficient communication of commongroups of parameters. This provides easy access to the parameters forHMI packages such as Lookout or BridgeVIEW. View objects easetasks such as loop tuning and configuration changes. There are fourstandard views defined by the FOUNDATION Fieldbus function blockspecification for each type of block. The specification includes whichparameters are contained in each view. The view objects are especially

Device Number 2Device Number 1

PID Block

BKCAL_INOUT

IN

AO Block

CAS_IN

BKCAL_OUT

OUT

AI Block

Note: The PID block could be in either device



useful if you are using the NI-FBUS Communications Manager API towrite your programs.

– VIEW_1 contains the main dynamic parameters.

– VIEW_2 contains the main static parameters relevant to theprocess.

– VIEW_3 contains the parameters from VIEW_1 and additionaldynamic parameters.

– VIEW_4 contains other static parameters, including configurationand maintenance parameters.

• Alert object—Alert objects allow a device to report alarms and eventsover the bus. Alert objects are fully configurable by the user.

• Trend object—Trend objects accumulate values of function blockparameters for access over the network and publish historical data forHMI trending and storage. They include the parameter’s value, status,and a timestamp. Multiple parameters in the same block can betrended. Other devices or hosts can make use of the informationaccumulated by the trend object.


3Fieldbus Communication

Scheduled Communication on the BusA device that sends data to other devices is called a publisher. A device thatneeds data from a publisher is called a subscriber. The Link ActiveScheduler uses the publisher/subscriber information to tell the publisherdevices when to transmit their data over the bus. These scheduled datatransfers are done in a deterministic manner (meaning that data istransferred between a given set of devices at the same time during each loopiteration), following the schedule developed in your configuration softwareand downloaded to the link masters.

The schedule can be divided into two parts: a function block schedulethat determines when a block executes, and a publishing schedule thatdetermines when data parameters are published over the Fieldbus.The function block schedule is downloaded to the particular devicethat contains each function block, and the publishing schedule isdownloaded to a device or devices that have link master capability.As discussed earlier, the link master currently executing the publishingschedule and thus controlling the process is the Link Active Scheduler.

Figure 3-1 shows the relationship of the function block schedule and thepublishing schedule to the device, link, link master, and Link ActiveScheduler. Note that the PC does not receive a function block schedulebecause it has no function blocks.

Chapter 3 Fieldbus Communication


Figure 3-1. Publishing and Function Block Schedules Relationships

Cascading BlocksSetting up a control strategy requires communication between functionblocks. For example, in a PID loop you would need an analog input block,a PID control block, and an analog output block. The data from the analoginput block must be fed to the PID control block. Additionally, data mustpass between the PID control block and the analog output block. Mostoften, these connections would be made in cascade mode.

Parameter Connections for Cascade ModeA cascade connection exists between two blocks: an upstream controllingblock, and a downstream controlled block. In a PID loop, the upstreamblock is the PID block, and the downstream block is the AO block. In thecase of cascaded PID blocks, the upstream PID feeds a setpoint into asecond PID that is acting as the downstream block. In both cases, theparameter connections are the same. The output (OUT) parameter of theupstream block is connected to the cascade input (CAS_IN) parameter ofthe downstream block. This connection controls the setpoint of thedownstream block. To allow the upstream block to determine the currentsetpoint of the downstream block, you must also connect the backwardcalculation output (BKCAL_OUT) parameter of the downstream block withthe backward calculation input (BKCAL_IN) of the upstream block. Theconnections are shown in the following figure.

Link Master(Receives the

Publishing Schedule)

Link

Basic Device(Receives theFunction Block

Schedule)

Basic Device(Receives theFunction Block

Schedule)

(Receives the FunctionBlock Schedule,

Publishing Schedule)

Link Active Scheduler

Chapter 3 Fieldbus Communication


Figure 3-2. Cascade Connections

Downstream

OUT CAS_IN

BKCAL_OUT

Upstream

BKCAL_IN


4Wiring and Connections

FOUNDATION Fieldbus wiring is similar to that used in traditional 4-20 mAsystems. Fieldbus uses existing 4-20 mA (twisted-pair) wiring to carrymultiple signals and power. It also uses existing terminal blocks. Liketraditional 4-20 mA systems, Fieldbus provides for intrinsic safetyrequirements that allow you to use Fieldbus in hazardous areas.

Note Not all devices support bus-powered operation. These devices will need their ownpower connections in addition to the two Fieldbus connections. One such device is theNational Instruments FP-3000.

The Fieldbus system provides for power supply redundancy and enablesloop-powered instruments. Unlike traditional 4-20 mA systems, Fieldbusallows you to connect field devices in parallel.

Table 4-1 describes the physical characteristics of an H1 FOUNDATION

Fieldbus network.

Table 4-1. Physical Overview of H1 FOUNDATION Fieldbus

Data Rate 31.25 Kbytes/s

Topology chickenfoot/crowsfoot,daisychain/spur, star

Bus Powering Possible? Yes, for devices that support it

Intrinsically Safe (IS) OperationPossible?

Yes, for devices that support it

Maximum Possible Number ofDevices Per Link WithoutRepeaters

32

Maximum Possible Cable LengthPer Link Without Repeaters

1900 m

Maximum Possible Spur Length 120 m

Chapter 4 Wiring and Connections


The following figure compares the wiring and hardware requirements ofFOUNDATION Fieldbus with those of traditional 4-20 mA systems. Noticethat the traditional system requires one intrinsic safety barrier and a set ofwires for each device, for a total of three barriers and three sets of wires.The FOUNDATION Fieldbus implementation requires only one intrinsic safetybarrier and one set of wires for multiple devices.

Figure 4-1. Intrinsic Safety in a FOUNDATION Fieldbus System

For more information on the Fieldbus wiring specification, see Wiring andInstallation 31.25 kbit/s, Voltage Mode, Wire Medium from the FieldbusFoundation (www.fieldbus.org). For a more readable document, see theFieldbus webpage of Relcom, Inc. (www.relcominc.com/fieldbus/).

TerminationYou must terminate your wiring in compliance with the FOUNDATION

Fieldbus specification. FOUNDATION Fieldbus requires a resistor and acapacitor in parallel. You must place termination appropriately on thenetwork, which will depend on your network topology. Refer to Wiring andInstallation 31.25 kbit/s, Voltage Mode, Wire Medium, or the Relcom, Inc.Wiring Design and Installation Guide.

FOUNDATIONFieldbus

Hazardous Area

4-20 mA

Computer

Controller

Computer

Intrinsically SafeBarrier


Input/OutputSubsystem





Link ConfigurationThere are several factors you should consider when deciding how manydevices to use on your H1 link.

• Link Topology—A FOUNDATION Fieldbus link can include one or morelinks joined by repeaters. Physically, one port on a NationalInstruments interface board connects to one link. Each individual linkcan be up to 1900 m and can have up to 32 devices connected. Up tofive individual links can be joined by four repeaters to make one largeaggregate link. This gives a maximum limit of about 155 devices perinterface. The connection to one interface port on the interface boardis viewed as one link by the NI-FBUS Configurator, regardless of howmany links might actually be joined by repeaters (important forsoftware licensing of the NI-FBUS Configurator). Refer to ChoosingConfiguration Software in Chapter 5, National Instruments FieldbusProducts, for information on ordering a link upgrade. NationalInstruments offers boards with one or two interfaces (ports).

Note Maximum Fieldbus link configurations (1900 m and 32 devices per link withoutrepeaters) cannot be achieved under many circumstances. Refer to the section LinkConfiguration for information on setting up your Fieldbus link.

• Bandwidth—A link can carry about 30 scheduled messages persecond. So, you could have three devices, each sending ten messagesper second, or 120 devices (connected by repeaters), each sending onemessage every four seconds.

• Power—Using bus powering reduces the number of devices that can beon one link. Additionally, the power supply on each link must besufficiently large. Some devices are separately powered (such as theNational Instruments FP-3000) and thus do not pull power from thelink’s power supply.

• Wire Resistance—Existing wire in older plants often has highresistance that can reduce the maximum link length.

• Barriers/Isolators—You should limit the power available in hazardousareas.



The following table illustrates the effect of intrinsically safe andbus-powered operation on the typical number of devices you can place onone link.

Table 4-2. Typical Number of Devices per Link

Bus SetupTypical Number of Devices(one link without repeaters)

Not Intrinsically Safe, Not BusPowered

2-32

Intrinsically Safe, Bus Powered 2-6 (of which 1-4 are in the ISarea)

Not Intrinsically Safe, BusPowered

2-12


5National Instruments FieldbusProducts

National Instruments provides both software and hardware for FOUNDATION

Fieldbus.

Hardware ProductsNational Instruments provides interface boards, both for the ISA bus(AT-FBUS) and PCMCIA (PCMCIA-FBUS). Each National Instrumentsboard comes with the NI-FBUS Communications Manager software,which the board uses to communicate over the bus.

The FP-3000 is a Fieldbus H1 device that, among other things, lets youintegrate legacy 4-20 mA devices into a FOUNDATION Fieldbus system.

Fieldbus roundcards are for developing Fieldbus devices. Contact Fieldbus,Inc. for purchasing information.

Software ProductsAll National Instruments Fieldbus software is developed for Windows NTbecause Windows 98/95 is less robust than Windows NT. NationalInstruments strongly suggests that you use a Windows NT system with theNational Instruments Fieldbus software.

The NI-FBUS Communications Manager software is used by the interfaceboards to communicate over the bus. Additionally, it provides a high-levelAPI advanced users can use to interface with the National InstrumentsFOUNDATION Fieldbus communication stack and hardware.

Most users use the NI-FBUS Configurator. In addition to providing thefunctionality of the NI-FBUS Communications Manager in a graphicalformat, it includes additional functionality to allow you to configure aFieldbus network. It can automatically generate the schedule for thenetwork and configure field devices and hosts to transmit and receivealarms and trends.

Chapter 5 National Instruments Fieldbus Products


The NI-FBUS Monitor helps you monitor and debug Fieldbus data traffic.It symbolically decodes data packets from the Fieldbus, monitors the livelist, and performs statistical analysis of packets. You can use the NI-FBUSMonitor to debug the development of device and host applications.

You can use FOUNDATION Fieldbus products with several NationalInstruments HMI software packages, including Lookout and BridgeVIEW.Communication with Lookout is handled directly by NIFB.EXE (theNI-FBUS process). For BridgeVIEW, LabVIEW, and other OPC clientprograms, the Fieldbus OPC server (included in NI-FBUS software) is usedfor communication.

Choosing Configuration SoftwareFOUNDATION Fieldbus links must be configured. Only with configurationsoftware can you do things like set device addresses, clear devices, anddownload (necessary if you are setting up a system for the first time). Yourconfiguration software must match the interface board your computer isusing to connect to the bus. National Instruments offers the NI-FBUSConfigurator with a National Instruments FOUNDATION Fieldbus interfaceboard to let you configure your Fieldbus links.

Interface boards and configuration software are sold separately becausemultiple interface boards can reside in the same computer. The NI-FBUSConfigurator, by default, is licensed for use on one machine, with up to fourFieldbus links (segments). If you have more than four links (ports on theboards), you need to purchase a link upgrade for each link in excess of four.To do so, download the order form from www.ni.com/fieldbus

Note The connection to one interface port on the interface board is viewed as one link bythe NI-FBUS Configurator, regardless of how many links might actually be joined byrepeaters (important for software licensing of the NI-FBUS Configurator).

If you only want to use the board to read and write values (not configure)and you are a programmer, you can make calls to the API in the NI-FBUSCommunications Manager and would not need the NI-FBUS Configurator.This would be possible only if you have already used a third party’shardware and configuration software to configure the link.



Choosing an HMI PackageNational Instruments offers a choice in industrial automation software.Both Lookout and BridgeVIEW provide flexible environments in whichyou can add innovative features to your application; however, in someapplication areas, one or the other might be the best solution for yourapplication.

Common Features of Both BridgeVIEW and LookoutBoth BridgeVIEW and Lookout provide the following functionality:

• OPC (OLE for Process Control) server and client capability.

• Driver support for PLCs (Programmable Logic Controller) connectedindependently of the Fieldbus.

• Access and control of your process through a web browser.

• Alarming and trending.

• High-speed data logging.

• Continuous, batch, and discrete process control.

Typical BridgeVIEW ApplicationsA typical BridgeVIEW application has the following features:

• Ideal for users familiar with LabVIEW who want to quickly developan industrial automation application.

• Ideal for applications that involve motion control, high-speed dataacquisition, or image acquisition.

• Ideal for applications that involve complex analysis. LabVIEWincludes a vast set of powerful virtual instrument (VI) libraries that canbe used for sophisticated calculations, analysis, or control.

Typical Lookout ApplicationsA typical Lookout application has the following features:

• An easy-to-use, no-programming interface. This is ideal for a largepercentage of industrial automation applications where monitoringand supervisory control is required, but advanced analysis is not.

• Online configuration to speed up development and debugging withouttaking down the process.

• Networking makes the development of client/server and multi-serverapplications straightforward.



• Built-in network security.

• Internal database makes it easy to share historical data, including alarmand event data, over the network.

• Native drivers are included for the most popular I/O devices andremote telemetry units (RTUs). Configuration of these drivers isbuilt-in.

Using Both BridgeVIEW and Lookout in an ApplicationIf you are interested in features from both packages, then you can use bothBridgeVIEW and Lookout in your application. A typical scenario for thiswould be when you want an easily-configurable interface to a remoteterminal unit with the capability of online configuration, but would alsolike to have some extensive analysis or interface with image acquisition ormotion control. You could use Lookout for the remote terminal unitconnectivity and BridgeVIEW for the analysis. Lookout and BridgeVIEWare both OPC-server and OPC-client capable. You could use the OPCconnectivity to exchange data between BridgeVIEW and Lookout.

© National Instruments Corporation A-1 Foundation Fieldbus Overview

ATechnical Support Resources

Web SupportNational Instruments Web support is your first stop for help in solvinginstallation, configuration, and application problems and questions. Onlineproblem-solving and diagnostic resources include frequently askedquestions, knowledge bases, product-specific troubleshooting wizards,manuals, drivers, software updates, and more. Web support is availablethrough the Technical Support section of www.ni.com

NI Developer ZoneThe NI Developer Zone at zone.ni.com is the essential resource forbuilding measurement and automation systems. At the NI Developer Zone,you can easily access the latest example programs, system configurators,tutorials, technical news, as well as a community of developers ready toshare their own techniques.

Customer EducationNational Instruments provides a number of alternatives to satisfy yourtraining needs, from self-paced tutorials, videos, and interactive CDs toinstructor-led hands-on courses at locations around the world. Visit theCustomer Education section of www.ni.com for online course schedules,syllabi, training centers, and class registration.

System IntegrationIf you have time constraints, limited in-house technical resources, or otherdilemmas, you may prefer to employ consulting or system integrationservices. You can rely on the expertise available through our worldwidenetwork of Alliance Program members. To find out more about ourAlliance system integration solutions, visit the System Integration sectionof www.ni.com

Appendix A Technical Support Resources

Foundation Fieldbus Overview A-2 www.ni.com

Worldwide SupportNational Instruments has offices located around the world to help addressyour support needs. You can access our branch office Web sites from theWorldwide Offices section of www.ni.com. Branch office web sitesprovide up-to-date contact information, support phone numbers, e-mailaddresses, and current events.

If you have searched the technical support resources on our Web site andstill cannot find the answers you need, contact your local office or NationalInstruments corporate. Phone numbers for our worldwide offices are listedat the front of this manual.

© National Instruments Corporation G-1 Foundation Fieldbus Overview

Glossary

Numbers4-20 mA system Traditional control system in which a computer or control unit

provides control for a network of devices controlled by 4-20 mAsignals.

AA Amperes.

Abstract Syntax Notation 1 A formal syntax description language that defines the exactformatting of FMS messages.

AC Alternating current.

Actuator A device that translates electrical signals into mechanical actions.

Acyclic communication Unscheduled communication on the bus.

A/D Analog-to-digital converter.

Address Character code that identifies a specific location (or series oflocations) in memory.

Administrative Function An NI-FBUS function that deals with administrative tasks, such asreturning descriptors and closing descriptors.

AI Analog Input.

Alarm A notification the NI-FBUS Communications Manager softwaresends when it detects that a block leaves or returns to a particularstate.

Alarm condition A notification that a Fieldbus device sends to another Fieldbus deviceor interface when it leaves or returns to a particular state.

Alert An alarm or event.

Alert function A function that receives or acknowledges an alert.

Alert objects Objects used for reporting alarms and events.

Glossary

Foundation Fieldbus Overview G-2 www.ni.com

All dynamic Information that is changing and may need to be referenced in adetailed display

Analog A description of a continuously variable signal or a circuit or devicedesigned to handle such signals.

Analog network A network that carries signals in analog form as a continuouslyvarying range of electrical voltage or current.

AO Analog Output.

API See Application Programmer Interface.

Application Function blocks.

Application clock An internal clock on the Fieldbus usually set to the local time orUniversal Coordinated Time. Application clock synchronizationallows the devices to time stamp data throughout the Fieldbusnetwork.

Application ProgrammerInterface

A message format that an application uses to communicate withanother entity that provides services to it.

Argument A value you pass in a function call. Sometimes referred to as aparameter, but this documentation uses a different meaning forparameter, which is included in this glossary.

Array Ordered, indexed list of data elements of the same type.

ASCII American Standard Code for Information Interchange.

ASN.1 Abstract Syntax Notation 1

Asynchronous Communication that occurs at times that are not predetermined.

AT-compatible Compatible with the 16-bit Industry Standard Architecture.

Attenuation Signal getting smaller as it travels on the cable.

Attribute Properties of parameters.

AWG American Wire Gauge.

Bb Bits.

B Bytes.

Backbone Another term for bus, the main wire that connects nodes.

Glossary


Bandwidth The range of frequencies present in a signal, or the range offrequencies to which a measuring device can respond.

Bank The combination of one FieldPoint network module and one or moreterminal bases and I/O modules.

Basic device A device that can communicate on the Fieldbus, but cannot becomethe LAS.

BG Bias Gain.

Bipolar signaling device A device that draws power from the cable for its internal operationand also draws an additional 10 milli-amps that it “wastes.”

Bit cell The length of time taken by a single bit. This time is 32 microsecondsfor H1 Fieldbus.

Bit time Time necessary to receive one bit.

Bitstring A data type in the object description.

Block A logical software unit that makes up one named copy of a block andthe associated parameters its block type specifies. The values of theparameters persist from one invocation of the block to the next. It canbe a resource block, transducer block, or function block residingwithin a virtual field device.

Block context Describes a category of NI-FBUS functions that accept blockdescriptors.

Block level The level of an NI-FBUS call that accepts a block descriptor.

Block tag A character string name that uniquely identifies a block on a Fieldbusnetwork.

Block view objects Variable list objects used to read multiple block parameters at once.

Boolean Logical relational system having two values, each the opposite of theother, such as true and false or zero and one.

Bridge An interface in a Fieldbus network between two different protocols.

BridgeVIEW A program for developing applications that require high channelcount datalogging, as well as supervisory control of distributedsystems.

Buffer Temporary storage for acquired or generated data.

Glossary


Bus The group of conductors that interconnect individual circuitry in acomputer. Typically, a bus is the expansion vehicle to which I/O orother devices are connected. Examples of PC busses are the ISA andPCI buses.

Bus scheduler See Link Active Scheduler.

CC Celsius.

Cable A number of wires and shield in a single sheath.

Capacitance The ability of a circuit (or device) to store electric energy in anelectric field.

Capacitor An electronic component that stores electrical charge. In a computer,capacitors are used in dynamic RAM cells and power supplies.

CCITT International Telegraph and Telephone Consultative Committee.

CD Compel Data.

CD schedule The CD schedule contains a list of activities that are scheduled tooccur an a cyclic basis.

Channel A pin or wire lead to which you apply or from which you read theanalog or digital signal.

Character string name See Tag.

Chickenfoot A common terminal block at a field junction box to which you canconnect field devices.

Circuit Interconnection of components to provide an electrical path betweentwo or more components.

CISPR International Special Committee On Radio Interference.

Client A device that sends a request for communication on the bus.

Client/server VCR type Used for queued, unscheduled, user-initiated, and one-to-onecommunication between devices on the Fieldbus.

Communication layer See Communication Stack.

Communication service Provides a standardized way for user applications (such as functionblocks) to communicate over the Fieldbus.

Glossary


Communication stack Performs the services required to interface the user application to thephysical layer.

Configuration device Device that generates all of the information needed to set up theFieldbus.

Configuration object See Linkage.

Connection Management The service the NI-FBUS Communications Manager provides byhandling Virtual Communication Relationships.

Contained parameter A parameter that does not receive or send data and is contained withina function block.

Context management service FMS service used to establish and release Virtual CommunicationRelationships with, and determine the status of, a virtual field device.

Control loop A set of connections between blocks used to perform a controlalgorithm.

Control strategy See function block application.

Controller An intelligent device (usually involving a CPU) that is capable ofcontrolling other devices.

ControlNet A 5 Mbit/sec communications protocol based on Producer/Consumertechnology.

Core Function The basic functions that the NI-FBUS Communications Managersoftware performs, such as reading and writing block parameters.

CPU Central processing unit.

Crowsfoot A common terminal block at a field junction box to which you canconnect field devices.

CS Control Selector.

Current The flow of electrons through a conductor.

Cyclic Closed-loop control.

DD/A Digital-to-analog converter.

Daisy-chain A wiring method where a number of devices are attached along thehomerun cable.

Glossary


Data Link Layer The second-lowest layer in the ISO seven-layer model (layer two).The Data Link Layer splits data into frames to send on the physicallayer, receives acknowledgment frames, and re-transmits frames ifthey are not received correctly. It also performs error checking tomaintain a sound virtual channel to the next layer.

Data link timesynchronization

A time distribution message broadcast on the Fieldbus so that alldevices have exactly the same data link time.

DataSocket National Instruments programming tool for sharing live measurementdata between applications separated by a network or the Internet.

dB Decibel.

DC Direct Current.

DC offset The change in input voltage required to produce a zero output voltagewhen no signal is applied to an amplifier.

DCS Distributed Control System.

DD See Device Description.

DDL See Device Description Language.

DDOD Device Description Object Dictionary. The Device Descriptionbinary file.

DDS See Device Description Service.

Deci-Bell A measurement of signal attenuation.

Descriptor A number returned to the application by the NI-FBUSCommunications Manager, used to specify a target for futureNI-FBUS calls.

Deterministiccommunication

A synonym for scheduled/cyclic communication. Communication inwhich data is transferred between a given set of devices at the sametime during each loop.

Device A sensor, actuator, or control equipment attached to the Fieldbus.

Device address A memory address that you use to access a device in a computersystem.

Device Description A machine-readable description of all the blocks and blockparameters of a device.

Glossary


Device DescriptionLanguage

A formal programming language that defines the parameters of theblocks. It also defines attributes of parameters and blocks like helpstrings in different languages, ranges of values for parameters, and soon.

Device Description Service A set of functions that applications use to access Device Descriptions.

Device ID An identifier for a device that the manufacturer assigns. No twodevices can have the same device ID.

Device level An NI-FBUS call that accepts a physical device descriptor.

Device tag A name you assign to a Fieldbus device.

DeviceNet A low-cost industrial network to connect industrial devices such aslimit switches, photoelectric cells, valve manifolds, motor starters,drives, and operator displays to PLCs and PCs.

DI Discrete Input.

Digital Pertaining to data (signals) in the form of discrete (separate/pulseform) integral values.

Directory A structure for organizing files into convenient groups. A directory islike an address showing where files are located. A directory cancontain files or subdirectories of files.

Distributed control Process control distributed among several devices connected bynetwork.

DLL See Dynamic Link Library.

DMA Direct Memory Access.

DO Discrete Output.

DRAM Dynamic Random Access Memory. Memory that requires electricityand refreshing to hold data.

Driver Device driver software installed within the operating system.

Dynamic Link Library A library of functions and subroutines that links to an application atrun time.

EEMI Electromagnetic interference.

End delimiter A bit sequence used to signal the end of a frame.

Glossary


E/P Electric-to-pneumatic converter

Ethernet A widely accepted and recognized industry standard local areanetwork.

Event An occurrence on a device that causes a Fieldbus entity to send theFieldbus event message.

Event service Event services allow the user application to report events and manageevent processing.

FFAS See Fieldbus Access Sublayer.

FB Function Block.

FBAP See Function Block Application.

FF FOUNDATION Fieldbus.

Field device A Fieldbus device connected directly to a Fieldbus.

Field equipment Sensors, actuators, and controllers.

Fieldbus An all-digital, two-way communication system that connects controlsystems to instrumentation. A process control local area networkdefined by ISA standard S50.02.

Fieldbus Access Sublayer The layer of the communication stack that provides an interfacebetween the DLL and layer seven of the OSI model. The FASprovides communication services such as client/server,publisher/subscriber, and event distribution.

Fieldbus cable Shielded, twisted pair cable made specifically for Fieldbus that hascharacteristics important for good signal transmission and are withinthe requirements of the Fieldbus standard.

Fieldbus Foundation An organization that developed a Fieldbus network specifically basedupon the work and principles of the ISA/IEC standards committees.

Fieldbus MessagingSpecification

The layer of the communication stack that defines a model forapplications to interact over the Fieldbus. The services FMS providesallow you to read and write information about the OD, read and writethe data variables described in the OD, and perform other activitiessuch as uploading/downloading data and invoking programs inside adevice.

Glossary


Fieldbus Network Address Location of a board or device on the Fieldbus; the Fieldbus nodeaddress.

FIP Factory Instrumentation Protocol.

FMS See Fieldbus Messaging Specification.

FOUNDATION Fieldbusspecification

The communications network specification that the FieldbusFoundation created.

FP-3000 National Instruments network interface module for the FieldPoint I/Osystem.

Frame A single transmission from a device.

FTP File Transfer Protocol.

Function block A named block consisting of one or more input, output, and containedparameters. The block performs some control function as itsalgorithm. Function blocks are the core components you control asystem with. The Fieldbus Foundation defines standard sets offunction blocks. There are ten function blocks for the most basiccontrol and I/O functions. Manufacturers can define their ownfunction blocks.

Function Block Application The block diagram that represents your control strategy.

Function Block ApplicationEditor window

The middle window of the NI-FBUS Configurator where you createyour block diagram.

Function block executionschedule

A list of times in the macrocycle when the function block will beginto execute its algorithm.

GGateway Fieldbus device that connects networks that use different

communication protocols, such as ControlNet-to-H1.

Ground An intentional or accidental conducting path between an electricalsystem or circuit and the earth or some conducting body acting inplace of the earth. A ground is often used as the common wiring pointor reference in a circuit.

Glossary


HH1 The 31.25 kbit/second type of Fieldbus.

H1 device An H1 device is a Fieldbus device connected directly to an H1Fieldbus. Typical H1 devices are valves and transmitters.

H2 Fieldbus FOUNDATION Fieldbus High Speed Ethernet (HSE) backbone networkrunning at 100 Mbit/second.

Hard code To permanently establish something that should be variable in aprogram.

HART Highway Addressable Remote Transducer. A digital communicationprotocol which operates on top of a conventional 4-to-20mA currentloop signal from a measurement device, such as a transmitter, or to avalve positioner.

Header file A C-language source file containing important definitions andfunction prototypes.

hex Hexadecimal. A base-16 numbering system which uses 0-9 and A-F.

HMI Human-Machine Interface. A graphical user interface for the processwith supervisory control and data acquisition capability.

Homerun A twisted-pair cable that connects the control room equipment with anumber of devices in the field.

Host device A computer or controller on a Fieldbus network.

HotPnP Hot Plug and Play.

HSE High Speed Ethernet.

Hz Hertz.

IIEC International Electrotechnical Commission. A technical standards

committee which is at the same level as the ISO.

Impedance Resistance.

in. Inches.

Glossary


Incremental DD Device description provided by device suppliers that references thestandard device descriptions. Incremental device descriptions mayinclude supplier-specific features such as calibration and diagnosticprocedures for their devices.

Index An integer that the Fieldbus specification assigns to a Fieldbus objector a device that you can use to refer to the object. A value in the objectdictionary used to refer to a single object.

Inductor Length of conductor used to introduce inductance into a circuit. Theconductor is usually wound into a coil to concentrate the magneticlines of force and maximize the inductance. While any conductor hasinductance, in common usage the term inductor usually refers to acoil.

Industrial network Standardized digital communications network used in industrialautomation applications; they often replace vendor-proprietarynetworks so that devices from different vendors can communicate incontrol systems.

Input parameter A block parameter that receives data from another block.

Intrinsic safety A characteristic of wiring or devices that cannot cause atmospheresto ignite or explode.

I/O Input/output.

IRQ Interrupt request.

IS See Intrinsic safety.

IS barrier A device used to keep voltages and currents on wires below the levelsthat can ignite an atmosphere.

ISA Industry Standard Architecture.

ISO International Organization for Standardization. A technical standardsorganization that creates international technical standards forcomputers and communications. The ISO is composed of nationalstandards organizations in 89 countries. The American NationalStandards Institute (ANSI) represents the United States in the ISO.

Isolation A type of signal conditioning in which you isolate the transducersignals from the computer for safety purposes. This protects you andyour computer from large voltage spikes and makes sure themeasurements from the devices are not affected by differences inground potentials.

Glossary


KKb Kilobytes.

Kbits Kilobits.

Kernel The set of programs in an operating system that implements basicsystem functions.

Kernel mode The mode in which device drivers run on Windows NT.

Keycode Code required from National Instruments to add links to a Fieldbusnetwork when using the NI-FBUS Configurator.

KHz Kilohertz.

km Kilometer.

LLabVIEW Laboratory Virtual Instrument Engineering Workbench—a program

development application based on the programming language G andused commonly for test and measurement purposes.

LAN Local Area Network.

LAS See Link Active Scheduler.

LED Light-emitting diode.

Lift-off voltage The initial voltage required for a Fieldbus device to start operating.

Link A FOUNDATION Fieldbus network is made up of devices connected bya serial bus. This serial bus is called a link (also known as a segment).

Link Active Schedule A schedule of times in the macrocycle when devices must publishtheir output values on the Fieldbus.

Link Active Scheduler The Fieldbus device that is currently controlling access to theFieldbus. A device that is responsible for keeping a link operational.The LAS executes the link schedule, circulates tokens, distributestime, and probes for new devices.

Link context Describes a category of NI-FBUS calls that accept link descriptors.

Link ID See Link identifier.

Link identifier A number that specifies a link.

Link master device A device that is capable of becoming the LAS

Glossary


Link object Link objects define the links between function block inputs andoutputs internal to the device and across the Fieldbus network.

Linkage A connection between function blocks.

Linkage object An object resident in a device that defines connections betweenfunction block input and output across the network. Linkage objectsalso specify trending connections.

Live list The list of all devices that are properly responding to the Pass Token.

LM Link Master.

Local Area Network A communications network that is limited in physical spatial area forthe purpose of easier connection of computers in neighboringbuildings.

Lookout National Instruments Lookout is a full-featured object-basedautomation software system that delivers unparalleled power andease of use in demanding industrial measurement and automationapplications.

Loop See control loop.

Mm Meters.

mA milliampere.

Macrocycle The least common multiple of all the loop times on a given link,or one iteration of a process control loop.

Manchester A coding method used for sending digital data on the Fieldbus.

Manufacturer’s identification An identifier used to correlate the device type and revision with itsdevice description and device description revision.

MAU Medium Attachment Unit.

Mbit Megabit.

M/E Mechanical-to-electric transducer.

Menu An area accessible from the command bar that displays a subset of thepossible command choices. In the NI-FBUS Configurator, refers tomenus defined by the manufacturer for a given block.

Glossary


Method Methods describe operating procedures to guide a user through asequence of actions.

ML Manual Loader.

mm millimeter.

Mode Type of communication.

Multicast To send a message to multiple destinations.

Multi-drop A transmission circuit with multiple terminals and peripherals. Couldalso be described as branches off a bus.

Multiplexer A switching device with multiple inputs that sequentially connectseach of its inputs to its outputs, typically at high speeds, in order tomeasure several signals with a single analog input channel.

NNetwork address The Fieldbus network address of a device.

Network Management A layer of the FOUNDATION Fieldbus communication stack thatcontains objects that other layers of the communication stack use,such as Data Link, FAS, and FMS. You can read and write SM andNM objects over the Fieldbus using FMS Read and FMS Writeservices.

Nifb.exe The NIFB process that must be running in the background for you touse your AT-FBUS or PCMCIA-FBUS interface to communicatebetween the board and the Fieldbus.

NI-FBUS API The NI-FBUS Communications Manager.

NI-FBUS CommunicationsManager

Software shipped with National Instruments Fieldbus interfaces thatlets you read and write values. It does not include configurationcapabilities.

NI-FBUS Configurator National Instruments Fieldbus configuration software. With it, youcan set device addresses, clear devices, change modes, and read andwrite to the devices.

NI-FBUS FieldbusConfiguration System

See NI-FBUS Configurator.

NI-FBUS process Process that must be running in the background for you to use yourAT-FBUS or PCMCIA-FBUS interface to communicate between theboard and the Fieldbus.

Glossary


NM See Network Management.

NMIB Network Management Information Base.

Node Junction or branch point in a circuit.

Non-scheduled/acycliccommunication

Communication that occurs at times that are not predetermined.

Non-volatile memory Memory that does not require electricity to hold data.

OObject An element of an object dictionary.

Object attribute A part of the machine-readable description of a Fieldbus object.

Object description Describes data that is communicated over the Fieldbus.

Object Dictionary A structure in a device that describes data that can be communicatedon the Fieldbus. The object dictionary is a lookup table that givesinformation such as data type and units about a value that can be readfrom or written to a device.

Object value The actual data value associated with a Fieldbus object.

Octet A single 8-bit value.

OD See Object Dictionary.

Offline Not connected to or installed in the computer.

OOS Out of Service mode.

OPC OLE for Process Control.

Operator acknowledgmentalarm

The verification an operator performs when he or she receives aFieldbus message.

OSI Open Systems Interconnect.

OSI Model Open Systems Interconnect Layered Communication Model. Acommunications protocol standard that the ISO created. It establishesa seven-layered framework for implementing protocols. In the OSImodel, control moves from one layer to the next in the followingmanner: control starts at the top layer in one station, moves throughall protocol layers to the bottom layer, then goes over the channel tothe next station and moves back up through all protocol layers.

Output parameter A block parameter that sends data to another block.

Glossary


PParameter One of a set of network-visible values that makes up a function block.

PC Personal Computer.

PCMCIA Personal Computer Memory Card International Association.

PD Proportional Derivative.

PDU Protocol Data Unit.

Peak-to-peak voltage A measure of signal amplitude; the difference between the highestand lowest excursions of the signal.

Physical device A single device residing at a unique address on the Fieldbus.

Physical device context Describes a category of NI-FBUS functions that accept physicaldevice descriptors.

Physical device tag A user-defined name for a physical device.

Physical Layer The layer of the communication stack that converts digital Fieldbusmessages from the communication stack to actual physical signals onthe Fieldbus transmission medium and vice versa.

PI Program Invocation.

PID Proportional/Integral/Derivative. A common control function blockalgorithm that uses proportions, integrals, and derivatives incalculation.

PLC See Programmable Logic Controller.

PN Probe Node.

Polarity Term used to describe positive and negative charges.

Poll To repeatedly inspect a variable or function block to acquire data.

Port A communications connection on a computer or remote controller.

POST Power-On Self Test.

Power conditioner Used to connect a conventional power source to a Fieldbus link.

PR Probe Response.

Preamble A bit sequence used to synchronize a signal receiver.

Process value A common Fieldbus function block parameter representing somevalue in the process being controlled.

Glossary


Program A set of instructions the computer can follow, usually in a binary fileformat, such as a .exe file.

Programmable LogicController

A device with multiple inputs and outputs that contains a programyou can alter.

PT Pass Token.

Publisher A device that has at least one function block with its output valueconnected to the input of another device.

Publishing schedule Determines when data members are published over the Fieldbus.

PV Process Value.

RRA Ratio.

Rack-mounted controller Controller mounted on a shelving unit in a chassis.

RAM Random-Access Memory.

RC Ratio Control.

Reflection An unwanted signal that results from a cable fault or impropertermination.

Repeater Boost the signals to and from the further link.

Resistance Opposition to current flow and dissipation of energy in the form ofheat.

Resistor Component made of material that opposes flow of current andtherefore has some value of resistance.

Resource block A special block containing parameters that describe the operation ofthe device and general characteristics of a device, such asmanufacturer and device name. Only one resource block per device isallowed.

Roundcard A hardware interface for developing FOUNDATION Fieldbus-compliantdevices.

Glossary


Ss Seconds.

Sample type Specifies how trends are sampled on a device, whether by averagingdata or by instantaneous sampling.

Scheduled/cycliccommunications

Communication that occurs at the same time during each controlcycle.

Segment See Link.

Sensor A device that responds to a physical stimulus (heat, light, sound,pressure, motion, flow, and so on), and produces a correspondingelectrical signal.

Server Device that receives a message request.

Service Services allow user applications to send messages to each otheracross the Fieldbus using a standard set of message formats.

Session A communication path between an application and the NI-FBUSCommunications Manager.

Session context Describes a category of NI-FBUS functions that accept sessiondescriptors.

Session level A category of NI-FBUS API calls that accepts a session descriptor.

Shield Metal grounded cover used to protect a wire, component or piece ofequipment from stray magnetic and/or electric fields.

Signal An extension of the IEEE 488.2 standard that defines a standardprogramming command set and syntax for device-specificoperations.

SMIB System Management Information Base.

Spur A secondary route having a junction to the primary route in anetwork.

Stack A set of hardware registers or a reserved amount of memory used forcalculations or to keep track of internal operations.

Stale Data that has not been updated for stale_limit number ofmacrocycles, where the stale limit is a parameter of the connection.

Start delimiter A bit sequence used to signal the start of the data portion of a frame.

Start FMS A service used to change the state from Idle to Running, and so on.

Glossary


Static library A library of functions/subroutines that you must link to yourapplication as one of the final steps of compilation, as opposed to aDynamic Link Library, which links to your application at run time.

Stub See Spur.

Subscribed parameter A block parameter that is receiving data.

Subscriber A device that has at least one function block with its input valueconnected to the output of another device.

Surge Large, unwanted voltage or current on wires. Generally caused bylightning or nearby heavy electrical power use.

Surge suppressor A device used to discharge surges to ground.

Symbol file A Fieldbus Foundation or device manufacturer-supplied file thatcontains the ASCII names for all the objects in a device.

System Management A layer of the FOUNDATION Fieldbus communication stack that assignsaddresses and physical device tags, maintains the function blockschedule for the function blocks in that device, and distributesapplication time. You can also locate a device or a function block tagthrough SM.

System ManagementConfiguration

Configuration parameters that set up device identification andnetwork time distribution.

TTag A name you can define for a block, virtual field device, or device.

TB Transducer Block.

TCP/IP Transmission Control Protocol/Internet Protocol. Thecommunications protocol used on the Internet.

TD Time Distribution.

Terminator A device used to absorb the signal at the end of a wire.

Thread An operating system object that consists of a flow of control within aprocess. In some operating systems, a single process can havemultiple threads, each of which can access the same data space withinthe process. However, each thread has its own stack and all threadscan execute concurrently with one another (either on multipleprocessors, or by time-sharing a single processor).

Glossary


Timeout A period of time after which an error condition is raised if some eventhas not occurred.

Token passing The LAS sends a Pass Token (PT) message to all devices in the livelist. The device is allowed to transmit unscheduled messages when itreceives the PT.

Tokenizer A program the Fieldbus Foundation provides that creates a binaryform of DDL code to ship to an end user with an instrument.

Traditional system See 4-20 mA system.

Transducer block A block that is an interface to the physical, sensing hardware in thedevice. It also performs the digitizing, filtering, and scalingconversions needed to present input data to function blocks, andconverts output data from function blocks. Transducer blocksdecouple the function blocks from the hardware details of a givendevice, allowing generic indication of function block input andoutput. Manufacturers can define their own transducer blocks.

Trend A Fieldbus object that allows a device to sample a process valueperiodically, then transmit a history of the values on the network.

Trend function An NI-FBUS call related to trends.

Trunk See Homerun.

UUCT Universal Coordinated Time.

Unipolar A signal range that is always positive (for example, 0 to +10 V).

Unscheduled Messages sent on the Fieldbus between transmissions of scheduledmessages.

Upstream Fewer network hops away from a backbone or hub. For example, asmall ISP that connects to the Internet through a larger ISP that hastheir own connection to the backbone is downstream from the largerISP, and the larger ISP is upstream from the smaller ISP.

User Layer The network layer of the communication stack above layer seven inthe OSI. The User Layer defines blocks and objects that represent thefunctions and data available in a device.

Glossary


VV Volts

Variable list A list of variables you can access with a single Fieldbus transaction.

VCR See Virtual Communication Relationship.

VDC Volts Direct Current.

VFD See Virtual Field Device.

VFD context Describes a category of NI-FBUS functions that accept virtual fielddevice descriptors.

View objects Predefined groupings of parameter sets that HMI applications use.

Virtual CommunicationRelationship

Preconfigured or negotiated connections between virtual fielddevices on a network.

Virtual Field Device The virtual field device is a model for remotely viewing datadescribed in the object dictionary. The services provided by theFieldbus Messaging Specification allow you to read and writeinformation about the object dictionary, read and write the datavariables described in the object dictionary, and perform otheractivities such as uploading/downloading data and invokingprograms inside a device. A model for remotely viewing datadescribed in the object dictionary.

WWaveform Multiple voltage readings taken at a specific sampling rate.

© National Instruments Corporation I-1 Foundation Fieldbus Overview

Index

AAI (Analog Input) block, 2-7alert object, 2-13AO (Analog Output) block, 2-7Automatic mode, 2-10

Bbasic device, 1-7blocks, 2-5 to 2-13

function blocks, 2-6 to 2-8AI (Analog Input) block, 2-7AO (analog Output) block, 2-7applications, 2-10CDO (Complex Discrete Output)

block, 2-8DI (Discrete Input) block, 2-7DO (Discrete Output) block, 2-7 to 2-8modes, 2-10 to 2-13parameters, 2-8 to 2-10PID (Proportional-Integral-Derivative)

block, 2-7standard function blocks (table), 2-6

resource block, 2-5transducer blocks, 2-5 to 2-6

bridge device, 1-7BridgeVIEW software, 5-3 to 5-4

CCascade mode, 2-10cascading blocks, 3-2 to 3-3

cascade connections (figure), 3-3parameter connections for Cascade

mode, 3-2CDO (Complex Discrete Output) block, 2-8

communication, 3-1 to 3-3cascading blocks, 3-2 to 3-3

cascade connections (figure), 3-3parameter connections for Cascade

mode, 3-2Fieldbus network overview, 1-3 to 1-4protocols, 1-4scheduled communication, 3-1 to 3-2

function block schedule and publishingschedule, 3-1 to 3-2

publisher/subscriber information, 3-1communication stack, 2-2 to 2-3

Data Link Layer, 2-2Fieldbus Access Sublayer, 2-2Fieldbus Messaging Specification

layer, 2-2 to 2-3virtual field devices, 2-3

Complex Discrete Output (CDO) block, 2-8configuration software, 5-2configuring links, 4-3 to 4-4connections. See wiring and connections.contained parameters for function

blocks, 2-8 to 2-10conventions used in manual, ivcustomer education, A-1

DData Link Layer, 2-2devices

basic device, 1-7bridge device, 1-7device descriptions, for user

layer, 2-4 to 2-5device ID, 1-6device tag, 1-6link master, 1-6 to 1-7

Index

Foundation Fieldbus Overview I-2 www.ni.com

DI (Discrete Input) block, 2-7DO (Discrete Output) block, 2-7 to 2-8documentation

conventions used in manual, ivrelated documentation, 1-1 to 1-2

FFieldbus. See FOUNDATION Fieldbus.Fieldbus Access Sublayer, 2-2Fieldbus Foundation, 1-2Fieldbus Messaging Specification

layer, 2-2 to 2-3Network Management, 2-3System Management, 2-3

FOUNDATION Fieldbuscommunication protocols, 1-4concepts in Fieldbus architecture,

1-5 to 1-10blocks and parameters, 1-8devices, 1-6 to 1-7linkages, 1-8links, 1-5loops, 1-8multiple loops, 1-9 to 1-10

definition of, 1-1Fieldbus network, 1-3 to 1-4uses of Fieldbus, 1-2 to 1-3

Function Block Application Process, 2-6function blocks, 2-6 to 2-8

AI (Analog Input) block, 2-7AO (Analog Output) block, 2-7applications, 2-10CDO (Complex Discrete Output)

block, 2-8DI (Discrete Input) block, 2-7DO (Discrete Output) block, 2-7 to 2-8function block and publishing schedule

relationships, 3-1 to 3-2

MODE_BLK parameter, 2-11modes, 2-10 to 2-13parameters, 2-8 to 2-10

example (figure), 2-9types of parameters, 2-8

PID (Proportional-Integral-Derivative)block, 2-7

standard function blocks (table), 2-6

Hhardware products, 5-1HMI software choices, 5-3 to 5-4

Iinput parameters for function

blocks, 2-8 to 2-10

Llayers. See also user layer.

components, 2-1OSI seven-layer communications model

(figure), 2-1physical layer, 2-2

Link Active Scheduler, 1-6 to 1-7, 3-1link master device, 1-6 to 1-7linkage object, 2-11 to 2-12

linkages example (figure), 2-12overview, 1-8

linksconfiguring, 4-3 to 4-4

factors to consider, 4-3typical number of devices per link

(table), 4-34Fieldbus network links, 1-5

Lookout software, 5-3 to 5-4

Index

© National Instruments Corporation I-3 Foundation Fieldbus Overview

loopscontrol loop (figure), 1-8definition, 1-8multiple loops

linkages between loops (figure), 1-10running at different rates (figure), 1-9

Mmacrocycle, in loops, 1-9manual. See documentation.Manual Mode, 2-10MODE_BLK parameter, 2-11modes, of function blocks, 2-10 to 2-11multiple loops

linkages between loops (figure), 1-10running at different rates (figure), 1-9

NNational Instruments Fieldbus

products, 5-1 to 5-4choosing configuration software, 5-2hardware products, 5-1HMI software choices, 5-3 to 5-4software products, 5-1 to 5-2

NI Developer Zone, A-1NI-FBUS Communications Manager

software, 5-1NI-FBUS Configurator software, 5-1NI-FBUS Monitor software, 5-2

Oobjects, 2-11 to 2-13

alert object, 2-13linkage object, 2-11 to 2-12trend object, 2-13view object, 2-12 to 2-13

Out Of Service mode, 2-10output parameters for function

blocks, 2-8 to 2-10

Pphysical layer, 2-2PID (Proportional-Integral-Derivative)

block, 2-7protocols for Fieldbus communication, 1-4published parameter, 2-12

Rresource block, 2-5

Sscheduled communication, 3-1 to 3-2

function block and publishing schedulerelationships, 3-1 to 3-2

publisher/subscriber information, 3-1software. See National Instruments Fieldbus

products.subscribed parameter, 2-12system integration, by National

Instruments, A-1

Ttechnical support resources, A-1 to A-2termination of wiring, 4-2transducer blocks, 2-5 to 2-6trend object, 2-13

Index

Foundation Fieldbus Overview I-4 www.ni.com

Uuser layer, 2-3 to 2-13

blocks, 2-5 to 2-13function block applications, 2-10function block modes, 2-10 to 2-13function block parameters,

2-8 to 2-10function blocks, 2-6 to 2-8resource block, 2-5transducer blocks, 2-5 to 2-6

device descriptions, 2-4 to 2-5objects, 2-11 to 2-13overview, 2-3 to 2-4

Vview object, 2-12 to 2-13virtual field devices, 2-3

WWeb support from National Instruments, A-1wiring and connections, 4-1 to 4-4

intrinsic safety in FOUNDATION Fieldbussystem (figure), 4-2

link configuration, 4-3 to 4-4physical overview of H1 FOUNDATION

Fieldbus network (table), 4-1termination, 4-2

Worldwide technical support, A-2

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